1. Field of the Invention
This invention relates to a scanning optical apparatus to be suitably used for a laser beam printer, a laser facsimile machine or the like.
2. Related Background Art
FIGS. 9 and 10 schematically illustrate a known scanning optical apparatus of the type under consideration. FIG. 9 is a schematic plan view of the apparatus, showing various parts arranged in an optical cabinet, and FIG. 10 is a schematic cross sectional view taken along line 10xe2x80x9410 in FIG. 9. As shown in FIGS 9 and 10, optical cabinet 1 contains therein a laser unit 2, a composite lens 3, a rotary polygon mirror 4, a drive motor 5, a first imaging lens 6, a second imaging lens 7 and a surface reflector (fold mirror) 8 along with other elements and the top opening of the optical cabinet 1 is covered by a lid 9. The laser unit 2 comprises a semiconductor laser beam source 2a, a collimator lens 2b, a photodetector section 2c and other components, while the composite lens 3 comprises a cylindrical lens 3a and a beam detecting lens 3b. The rotary polygon mirror 4 is provided with deflection/reflection planes 4a and driven to rotate by the drive motor 5.
As seen from FIGS. 9 and 10, the first imaging lens 6 is rigidly secured to the optical cabinet 1 by means of a pair of leaf springs 10, 11 and the second imaging lens 7 is rigidly secured to the optical cabinet 1 also by means of a pair of leaf springs 12, 13. The leaf springs 10 through 13 are arranged in respective spring securing sections 14, 15, 16, 17 of the optical cabinet located at the light exiting sides of the imaging lenses 6, 7 so that the latter are urged toward the light entering sides thereof.
The first imaging lens 6 is typically provided with;upper and lower flange sections 6a, 6b of which the lower flange section 6b have a projection 6c projecting from the longitudinal center thereof for the purpose of centering the first imaging lens 6. Additionally, the first imaging lens 6 is provided at the longitudinal opposite ends thereof with respective upright direction reference planes 6d, 6d that are arranged at the lower flange section 6b, while an optical axial direction reference plane 6e is arranged at the light entering side of the lens 6.
The optical cabinet 1 is provided with an opening 1a for allowing the laser beam reflected by the surface reflector 8 to pass therethrough, a pair of positioning pins 1b, 1b for pinching the projection 6c of the first imaging lens 6, an upright direction reference section 1c on which the upright direction reference planes 6d, 6d of the first imaging lens 6 abut, a rib-shaped optical axial direction reference section 1d on which the optical axial direction reference plane 6e of the first imaging lens 6 abuts and an anchor claw for anchoring the leaf springs 10.
The leaf spring 12 is made to show a profile that corresponds to that of the second imaging lens 7 and the leaf springs 11, 13 are arranged symmetrically relative to the corresponding leaf springs 10, 12. Additionally, the spring securing section 16 is made to show a profile that corresponds to that of the leaf spring 12 and the spring securing sections 15, 17 are arranged symmetrically relative to the corresponding spring securing sections 14, 16.
With the above described known optical scanning apparatus, a total of four leaf springs 10 through 13 having respective profiles that are different from each other are required in order to rigidly secure the imaging lenses 6, 7 to the optical cabinet 1. So many leaf springs may by turn require a large number of assembling and disassembling steps and cumbersome control procedures. Additionally, since the spring securing sections 14 through 17 are respectively subjected to the reactions of the urging forces of the leaf springs 10 through 13, large power is required when, fitting the leaf springs 10 through 13 to the optical cabinet 1.
In view of the above identified problems of the prior art, it is therefore the object of the present invention to provide an optical scanning apparatus that comprises a reduced number of components and whose imaging lenses can be mounted and dismounted with ease.
According to the invention, the above object is achieved by providing a scanning optical apparatus comprising a light emitting means adapted to emit a laser beam, a deflection means for deflecting the laser beam from said light emitting means and a pair of imaging lenses adapted to scan a photosensitive member by the laser beam from the deflection means, the abutment reference planes of the optical axial direction of said imaging lenses being arranged at the back sides of said imaging lenses relative to the oppositely disposed respective surfaces of the lenses.
In another aspect of the invention, there is provided a scanning optical apparatus comprising a light emitting means adapted to emit a laser beam, a deflection means for deflecting the laser beam from said light emitting means and a pair of imaging lenses adapted to scan a photosensitive member by the laser beam from the deflection means, the abutment reference planes of the optical axial direction of said imaging lenses being arranged at the oppositely disposed respective surfaces of the lenses.
In still another aspect of the invention, there is provided a scanning optical apparatus comprising a light emitting means adapted to emit a laser beam, a deflection means for deflecting the laser beam from said light emitting means, first and second imaging lenses adapted to scan a photosensitive member by the laser beam from the deflection means and an urging member for urging said first and second imaging lenses, said urging member being adapted to urge said second imaging lens in a direction opposite to the direction of urging said first imaging lens.
In a further aspect of the invention, there is provided a scanning optical apparatus comprising a light emitting means adapted to emit a laser beam, a deflection means for deflecting the laser beam from said light emitting means, first and second imaging lenses adapted to scan a photosensitive member by the laser beam from the deflection means and an urging member for urging said first and second imaging lenses, said urging member being adapted to urge one or more than one optical components in addition to urging said first and second imaging lenses.